The music production industry typically consists of artists and producers working in a studio to create an audio stream reflecting what the music sounds like when played “live”. The human voice and most instruments generates a dynamic sound which varies in loudness as the piece of music varies in frequency, pace and intensity. The studio recording typically reflects this dynamic sound and thus varies in loudness.
The ratio between the loudest portion of an audio stream and the least loud portion is known as the Dynamic Range (DR) of the audio stream. The human ear can potentially hear a very high dynamic range, exceeding 100 dB, but the ability to appreciate the DR is dependent upon the ambient noise. With very little ambient noise, humans can hear and appreciate music with very large variance in loudness.
Music with full DR is preferably heard in a noise free ambient environment, such that the even the least loud portions of the music can be heard and appreciated. However, listening to music in a noise free environment is very unusual to date. An ever increasing amount of music is consumed in portable device in any environment, in car stereos with surrounding noise, or as background music while keeping a conversation.
Listening to music with a very high DR in a noisy environment results some portions of the music not being heard, as these portions are less loud than the noise. Therefore a need exist of adjusting the loudness of the music, such that all portions of the music are heard through the ambient noise, and not only the loud portions.
This adjustment is called mastering and is performed by a Mastering Engineer (ME) who is a person skilled in adapting the audio/music for distribution. As the same audio stream is to be played in high-end stereos and cheep clock-radios, the mastered version is typically a significantly compressed version which looses DR in favor of loudness. The end consumer owning a high-end stereo cannot benefit from the potential as the audio stream with the Dynamic Range Compression (DRC) does not retain the original high DR. Popular music typically has a DR of 6-10 dB, with some forms of music having as little as 1-5 dB.